FORTE observations of simultaneous VHF and optical emissions from lightning: Basic phenomenology

Abstract

Abstract. Preliminary observations of simultaneous VHF and optical emissions from lightning as seen by the Fast on-Orbit Recording of Transient Events (FORTE) spacecraft are presented. VHF/optical waveform pairs are routinely collected both as individual lightning events and as sequences of events associated with cloud-to-ground (CG) and intracloud (IC) flashes. CG pulses can be distinguished from IC pulses on the basis of the properties of the VHF and optical waveforms but mostly on the basis of the associated VHF spectrograms. The VHF spectrograms are very similar to previous ground-based HF and VHF observations of lightning and show signatures associated with return strokes, stepped and dart leaders, attachment processes, and intracloud activity. For a typical IC flash, the FORTE-detected VHF is generally characterized by impulsive broadband bursts of emission, and the associated optical emissions are often highly structured. For a typical initial return stroke, the FORTE-detected VHF is generated by the stepped leader, the attachment process, and the actual return stroke. For a typical subsequent return stroke, the FORTE-detected VHF is mainly generated by dart leader processes. In remedy of this situation the Fast on-Orbit Recording of Transient Events (FORTE) satellite was launched on August 29, 1997. FORTE is a joint Los Alamos National Laboratory and Sandia National Laboratories satellite experiment that was primarily designed to address technology issues associated with treaty verification and the monitoring of nuclear tests from space. The satellite carries VHF broadband radio receivers and an Optical Lightning System (OLS) which are optimally designed for the detection of lightning transients. The design of this instrumentation and its availability for continuous scientific use makes FORTE an ideal space platform from which to monitor and study the simultaneous emission of VHF and optical radiation from lightning. This paper reports on the preliminary phenomenology and analysis of the correlated FORTE VHF and optical data sets.The goals of this study are twofold: (1) to demonstrate the utility of using a dual phenomenology approach for the remote 2191

Revisiting "Narrow Bipolar Event" intracloud lightning using the FORTE satellite

“…Further observations on NBEs and their associated VHF TIPPs were presented in publications based on FORTE (Jacobson, 2003a, b;Jacobson and Light, 2003;) and on LASA Jacobson et al, 2007;Suszcynsky and Heavner, 2003;Wiens et al, 2008). Recently it has been shown that the VHF pulse in the TIPP associated with NBEs is neither polarized nor coherent (Jacobson et al, 2011).…”

“…This ground-truth campaign allowed 392 A. R. Jacobson and T. E. L. Light: Revisiting "Narrow Bipolar Event" intracloud lightning the unambiguous identification of radio signatures that are characteristic of various stroke types (positive and negative cloud-to-ground, or +CG and −CG; intracloud, or IC; etc.). This ground-truthing by NLDN allowed development of a rudimentary identification of stroke type from the FORTErecorded radio waveform alone (Suszcynsky et al, 2000).…”

“…These sferics were sampled over several millisec, with a sampling rate of 1 Megasamples/s. These waveform recordings were extremely useful for studying characteristics of lightning discharges, including NBEs Jacobson and Heavner, 2005;Jacobson et al, 2007;Smith et al, , 2004Suszcynsky and Heavner, 2003). Indeed, the only completely reliable way of identifying a sferic as being due to an NBE is to examine details of its recorded waveform from several stations.…”

“…This particular dual-channel receiver system was in full operation by December 1997; it failed in December 1999, after which FORTE used a single-channel, 85-MHz-bandwidth receiver. More details are available elsewhere Jacobson and Shao, 2002;Shao et al, , 2005Jacobson, 2001, 2002;Suszcynsky et al, 2000).…”

Lightning detection on Venus: a critical review

“…A combination of an ELF electrical/magnetic detection with another type (most obviously an optical sensor, but possibly gamma ray, or even VHF radio) would be much more compelling (as performed on FORTE and C/NOFS at Earth-see, e.g., Fig. 5) and Suszcynsky et al 2000. As noted by Russell (2011), a low circular polar orbit is desirable for radar mapping, and a modest lightning instrument would be a valuable but relatively inexpensive augmentation to a radar mapping mission.…”